The present invention relates to antennas and in particular, to radio frequency antennas for transmitting and receiving radio frequency (RF) signals. Even more particularly, the present invention relates to a compact antenna, which is provided for use in connection with a radio frequency controlled lighting control system. In particular, the present invention relates to an antenna which is provided on a lighting control device, for example, a light dimmer, and which receives and/or transmits radio frequency signals for controlling a lamp and communicating status of the lamp, for example, on, off, and intensity level. The radio frequency signals are used to control from a remote master location the status of the lamp connected to the light dimmer and also to provide information back to the master location concerning the status of the controlled lamp. The device at the master location may also employ an antenna according to the invention.
The invention also relates to a control device employing the antenna that can be mounted in a standard electrical wall box. In particular, the invention relates to a local electrical control device capable of remotely controlling one or more electric lamps and adapted to be mounted in a standard electrical wall box and receiving and transmitting signals via the antenna. The invention further relates to a master control device capable of remotely controlling one or more local electrical control devices and adapted to be mounted in a standard electrical wall box and employing the antenna to transmit to and receive signals from a local electrical control device which responds to the control signals from the master device.
Although the present invention is directed to an antenna for use in a lighting control system, the antenna of the present invention can be applied to the communication of signals relating to the control and status of other devices, for example, communication equipment, motors, security systems, appliances, HVAC systems (heating, ventilating, and air conditioning) and other devices.
The present invention is directed to an antenna of compact design which can be included within the lighting control device, for example a light dimmer, and which fits into a standard electrical wall box. The invention is also directed to a lighting control device itself, either a master or local (remote) unit. The invention is of particular use in a system which uses radio frequency signals to control the status of controlled electrical devices such as electric lamps. In such a system, the conventional manually controlled hard wired lighting control devices, for example, wall switches and dimmers, are replaced by control devices having a control circuit and an antenna according to the present invention. The system in which the antenna according to the present invention is used may thus be provided to enable an existing building lighting system (or other electrical/electronic devices) to be controlled remotely from various locations without requiring hard wiring of the building to incorporate the necessary control wiring to accomplish remote control of lighting fixtures or other devices. Accordingly, in a system in which the antenna of the present invention is used, the lighting control device, for example, a light dimmer which replaces the conventional light switch/dimmer, contains an antenna according to the present invention, the necessary actuators for accomplishing manual control of the lighting fixture, as well as a control circuit and RF circuit for allowing remote control via signals received and transmitted by the antenna of the lighting control device. The antenna and control device fit within a standard electrical wall box allowing the conventional lighting control device to be removed and replaced by the lighting control device according to the invention. Similarly, a master unit according to the invention having actuators thereon and an antenna for transmitting signals to the local control devices and receiving status signals from the local control device is also adapted according to one embodiment of the invention, to be disposed in a conventional electrical wall box.
In accordance with the present invention, the antenna is of compact size such that it fits within the standard electric wall box together with the control device electronic circuitry and mechanical components and is a part of the electrical control device for controlling the lamp.
In addition, although the control device employing the antenna of the present invention has been described in connection with its use in replacing conventional, non-radio frequency controlled lighting control devices, the present invention can also be employed in new construction so that the number of wires that need to be routed in the new construction can be reduced. Accordingly, in the system employing the present invention, it is not necessary to run control wires (only the electrical power wires need to be installed) to control the lighting system since the antenna of the present invention will and receive transmit radio frequency signals to accomplish this control.
There is presently a system known in the prior art that allows for remote control of lamps without hard wiring the control wires to the lighting control devices. This known system is the Lutron Radio RA system in which lamps are controlled remotely by radio frequency signals. In the Radio RA system, each lighting control device, in addition to manual controls, has a transceiver and an antenna, which receives and transmits radio frequency signals from and to a master control unit. At the master control unit, the status of the various lamps in the building structure can be remotely controlled, that is, the on, off and intensity level status can be controlled from the master control unit by sending RF signals from the master device to the lighting control devices. In order to ensure that radio frequency signals are transmitted to and from all devices in the system, repeaters are employed as necessary. Patents describing the Radio RA System include U.S. Pat. Nos. 5,905,442 and 5,848,054, among others.
In the existing Radio RA system, a compact radio antenna is used which comprises a planar antenna. That planar antenna, although satisfactory, has a number of disadvantages. One of the problems with the prior art antenna is that it is relatively expensive to make, requiring inductive patterns disposed on the printed circuit board determining the frequency of resonance. These planar antennas are somewhat expensive to manufacture. In addition, the antenna of the prior art device is relatively large in size, being substantially coextensive with the electrical box opening. Further, it is desirable to increase the transmission range of the antenna of the prior art device. Furthermore, the prior art device requires substantial insulation because the antenna is connected to the AC line (or “line voltage”) and is thus at the same electrical potential. Line voltage is approximately 120 VRMS in the United States, for example, and varies throughout the countries and regions of the world. Accordingly, to provide user protection from electrical shock, the planar antenna of the prior art device requires substantial insulation members. Because the planar antenna is relatively large and because it is electrically connected to the line voltage of the dimmer, more insulation is needed when using the planar antenna, thus increasing the cost of the dimmer. The antenna of the prior art device is described in U.S. Pat. Nos. 5,982,103 and 5,736,965.
It is thus desirable to provide an antenna, which offers increased performance characteristics, requires less insulation or is isolated from the AC line, and is smaller and less expensive to make.